- What actions does Windows take when I "Offline" a disk in the Disk Management GUI?
- What actions does Windows take when I "Offline" a disk in Diskpart?
- Are there any differences between the two scenarios?
They work the same. One thing to note is sometimes the two can get out of sync. In that case you'll need to restart the logical disk management service and restart at least the GUI.
(I feel that the cli version is less likely to trip in that situation, but it's also been a while since I last managed to sufficiently break things.)